Freight trains are typically wider than passenger trains. For stations to accommodate both types of trains, it is therefore necessary to effectively widen the passenger platform for passenger trains, so that the platform meets the train. Conversely, in order to allow freight trains to pass, the platform must be narrowed. One solution to this variable-width platform need is to attach a retractable platform edge extension to the fixed platform. Such platform edge extensions have been designed to pivot between a closed position, in which the extension is aligned with the platform edge, with its top closely matching and effectively continuing the top of the platform, and an open, or retracted, position, in which the platform extension is pivoted up to rest on the top of the platform, extending at just over 90.degree. from the platform top.
The platform edge extension pivoting has been accomplished by including a number of spaced, protruding plates attached to the underside of the edge extension and extending under the platform when the edge extension is in the open position. That platform edge extension pivoting member plate is received in the center of a pair of spaced plates fixed to the underside of the fixed platform, with one of the fixed plates on each side and closely adjoining the edge extension pivoting plate. A bolt is passed through the two fixed plates and through a hole in the edge extension pivoting plate to provide an axis on which the platform edge extension can pivot.
Because this pivot axis is below the platform, the pivoting plate must be able to pass through the upper surface of the platform when the edge extension is pivoted from the open to the closed position. Accordingly, it has been necessary to cut slots in the platform which are a bit wider than the pivoting plate and aligned with the pivoting plate; this allows the plate to move through and above the platform during movement of the edge extension from the closed to the open position. There are typically three or four such pivoting-member receiving slots in the platform for every ten or fifteen foot section of the platform edge extension.
These slots partially defeat the objective of an absolutely safe platform. They present a tripping hazard, and an area in which objects such as wheelchair wheels and women's shoe heels can get caught. Additionally, the slots can become fouled with dirt and the like, making the pivoting operation of the platform more difficult. Since these platform extensions are balanced so that a single man can move a platform between the open and closed positions, this fouling can present a substantial impediment to proper platform extension movement. It is of critical importance that the extension be lifted before the passage of a freight train- if a platform extension is left in the closed position when a freight train passes, the impact can cause severe damage to the platform edge extension, the platform, and the train itself. Also, broken pieces of impacted platforms travelling through the station at extremely high speeds caused by the impact have been known to injure or kill passengers in the station. Accordingly, there exists a substantial need for such a pivoting platform extension which can pivot in the same fashion without the need for slots in the platform.
It would also be desirable to design platform extensions so that potential pedestrian hazard, damage to the sections, and damage to trains, is minimized if a platform is left in the closed position and is struck by a freight train. The rigid nature of the platform extensions has caused extensive damage to both the platform extension and the train in platform extension impacts which have occurred to date. Also, as mentioned above, pieces of the impacted platform can travel substantial distances from the impact site, causing pedestrian injury and additional station damage.